The junction between the ileum and colon fufills conventional criteria for classification as a sphincter (ileo-cecal sphincter; ICS); it exhibits a high pressure zone which relaxes with proximal distention, contracts with distal distention and has muscle which displays specialized functions in vitro. However, the physiology and functional role of the ICS in controlling the flow of chyme from small to large intestines have received little attention. And yet, by regulating the entry of contents into the colon, the ICS could by an important determinant of colonic function and be relevant to diseases characterized by colonic dysfunction. We have developed a canine preparation which allows long term recording of electrical control activity in the ileum and ICS in association with changes in intraluminal pressures; we will use a sphincteric "sleeve probe" for recording ICS tonic pressure. A parallel series of studies will be performed in intact man, we will record in man ileocolonic and ICS pressures. A major aim is to establish the temporal correlations among interdigestive myoelectrical control activity (IMC's) and the pressure forces that operate at the ICS. Thereafter, these potentially propulsive and retarding forces will need to be integrated with transit of liquids and solids through the ileum and across the ICS. Our ultimate goal is to establish the mechanisms that control ileocolonic transit in health so as to develop a basis for evaluating the relationships of disturbed function of the ICS to human disease. We also wish to examine ways in which functions of the ICS might be modified for potential therapeutic benefits.